In a wireless local area network (Wireless Local Area Network, WLAN) institute of electrical and electronic engineers (Institute of Electrical and Electronic Engineers, IEEE) 802.11 orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) system, a pilot frequency is mainly used for carrying out sampling frequency synchronization and residual phase tracking. A receiving terminal will produce a fractional offset in the sampling, sampling frequency correction must be carried out in the frequency domain by the pilot frequency, the data after carrier frequency offset correction still has certain residual deviations, these residual deviations will cause a phase shift of the data, and residual phase tracking is carried out by the pilot frequency. The sampling frequency deviation on a pilot frequency subcarrier is equivalent to the sampling of the frequency deviation on each subcarrier, and on the premise of the same sample number and equal intervals, the more uniform the sample sampling distribution is, the better the overall actual situation can be represented.
Due to the presence of null subcarriers in the IEEE 802.11 system, the pilot frequencies are non-uniformly inserted, but the interval between the pilot frequencies is consistent or is selected on the basis of the consistent interval. In the IEEE 802.11ad protocol (2.16 GHz bandwidth), there are 512 subcarriers in total in each OFDM symbol, which are distributed on −256 to 255 positions, wherein there are 16 pilot frequency subcarriers, the positions thereof are respectively {±10, ±30, ±50 , ±70, ±90, ±110, ±130, ±150}, and the interval of the pilot frequency subcarriers is 20.
In the IEEE 802.11 OFDM system, the pilot frequency is mainly used for carrying out sampling frequency synchronization and residual phase tracking. The smaller the difference between an estimated sampling frequency deviation and a pre-added sampling frequency deviation is, the smaller the difference between a residual phase deviation and a pre-added residual phase deviation is, the more accurate the estimation is, and the improvement of performance is reflected in the wireless system.